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Abstract

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​Assessing the potential of marine organisms to adapt genetically to increasing oceanic CO2
levels requires proxies such as heritability of fitness-related traits
under ocean acidification (OA). We applied a quantitative genetic method
to derive the first heritability estimate of survival under elevated CO2
conditions in a metazoan. Specifically, we reared offspring, selected
from a wild coastal fish population (Atlantic silverside, Menidia menidia), at high CO2
conditions (~2300 μatm) from fertilization to 15 days posthatch, which
significantly reduced survival compared to controls. Perished and
surviving offspring were quantitatively sampled and genotyped along with
their parents, using eight polymorphic microsatellite loci, to
reconstruct a parent–offspring pedigree and estimate variance
components. Genetically related individuals were phenotypically more
similar (i.e., survived similarly long at elevated CO2
conditions) than unrelated individuals, which translated into a
significantly nonzero heritability (0.20 ± 0.07). The contribution of
maternal effects was surprisingly small (0.05 ± 0.04) and
nonsignificant. Survival among replicates was positively correlated with
genetic diversity, particularly with observed heterozygosity. We
conclude that early life survival of M. menidia under high CO2
levels has a significant additive genetic component that could elicit
an evolutionary response to OA, depending on the strength and direction
of future selection.